2025 Volume 46 Issue 3 Pages 127-137
The Tg -disappearing phenomenon in the glass transition region is examined by analyzing viscoelastic properties of highly crosslinked samples of cured epoxy resin. A structure parameter related to the degree of crosslinking of the network structure is derived in a simple statistical mechanical model. Molecular weight of the relaxation element can be estimated from the maximum value of the loss rigidity curve for each relaxation mode by using this model. It is confirmed for epoxy samples that decrease of molecular weight of the linear segment bound with crosslinking units and increase of molecular weight of the relaxation element at the glass transition point are caused with increase of the degree of crosslinking. Tgdisappearing phenomenon is concluded to relate closely with molecular weight difference of relaxation elements for neighboring relaxation processes.
